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COG6
component of oligomeric golgi complex 6
COG6 is located on the long (q) arm of chromosome 13, at band 13q14.11. Arm ratio per GRCh38 - banding schematic.
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Overview
COG6 is located on chromosome 13 and produces a 657-amino acid protein that functions as one of eight subunits forming the COG complex. This molecular machinery plays a central role in maintaining Golgi apparatus integrity and coordinating the retrograde transport of glycosylation enzymes within the cell. The Golgi apparatus serves as the primary site where newly synthesised proteins undergo post-translational modifications, particularly the addition of complex sugar chains through glycosylation. When COG6 function is impaired, these glycosylation processes become disrupted, resulting in a range of clinical manifestations affecting multiple organ systems. Pathogenic variants in this gene follow an autosomal recessive inheritance pattern, meaning that affected individuals typically inherit two altered copies, one from each parent.
What the gene does
The COG6 protein operates within the conserved oligomeric Golgi complex, an octameric assembly that coordinates vesicle tethering and membrane trafficking in the Golgi apparatus. This complex ensures that glycosylation enzymes remain properly localised within distinct Golgi compartments, enabling the sequential addition and modification of sugar residues on proteins and lipids. COG6 specifically contributes to the structural integrity of the complex and facilitates the retrograde retrieval of glycosyltransferases and other enzymes from later Golgi compartments back to earlier ones. This recycling mechanism maintains the compartment-specific distribution of enzymes necessary for ordered glycosylation reactions. When COG6 is absent or non-functional, the spatial organisation of glycosylation machinery becomes disrupted, leading to abnormal glycan structures on cellular proteins. Such defects compromise the stability, trafficking and function of numerous glycoproteins throughout the body, explaining the multi-system features observed in individuals with COG6-related conditions.
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Chromosome location
COG6 is positioned on the long arm of chromosome 13 at band 13q14.11. This chromosomal region contains multiple genes involved in diverse cellular processes. The COG6 gene spans genomic DNA and encodes a transcript that is translated into a protein of 657 amino acids.
Protein structure
Domain architecture has not been experimentally characterised in detail for this protein. The COG6 protein interacts with seven other COG subunits to form two distinct lobes within the complete complex, and structural studies suggest that COG6 contributes to the lobe B portion of the assembly alongside COG5, COG7 and COG8.
Key variants
Pathogenic variants in COG6 typically result in loss of protein function through mechanisms including premature termination, frameshift alterations and missense changes that destabilise the protein or disrupt its interactions with other COG subunits. Because the gene follows autosomal recessive inheritance, disease manifestations generally occur only when both gene copies carry pathogenic variants. The variant spectrum includes both null alleles that eliminate protein production and hypomorphic variants that retain partial function.
Sample of pathogenic variants
10 pathogenic / likely-pathogenic variants from ClinVar, ranked by review status (expert-panel-reviewed first). This is a sample; recurrent founder variants in a specific population may not appear here - see the full ClinVar listing via the link above.
| Variant (HGVS) | Protein change | Classification | Evidence | Associated condition |
|---|---|---|---|---|
c.1078C>T | p.Arg360Ter | Pathogenic/Likely pathogenic | ★★☆☆ | COG6-congenital disorder of glycosylation |
c.1167-24A>G | - | Pathogenic/Likely pathogenic | ★★☆☆ | Hypohidrosis-enamel hypoplasia-palmoplantar keratoderma-intellectual disability syndrome |
c.1535T>G | p.Leu512Ter | Pathogenic/Likely pathogenic | ★★☆☆ | COG6-congenital disorder of glycosylation |
c.511C>T | p.Arg171Ter | Pathogenic | ★★☆☆ | COG6-congenital disorder of glycosylation |
c.548dup | p.Lys184fs | Pathogenic/Likely pathogenic | ★★☆☆ | COG6-congenital disorder of glycosylation |
c.651_654del | p.Leu217fs | Pathogenic | ★★☆☆ | COG6-congenital disorder of glycosylation |
c.984_994del | p.Leu329fs | Pathogenic/Likely pathogenic | ★★☆☆ | COG6-congenital disorder of glycosylation |
c.1009+1G>T | - | Pathogenic | ★☆☆☆ | COG6-congenital disorder of glycosylation |
c.248del | p.Ser83fs | Pathogenic | ★☆☆☆ | Fetal anomalies with a likely genetic cause |
c.686G>A | p.Trp229Ter | Pathogenic | ★☆☆☆ | Hypohidrosis-enamel hypoplasia-palmoplantar keratoderma-intellectual disability syndrome |
Evidence stars indicate ClinVar review status. Individual variant interpretation should always be performed by a qualified clinical laboratory - many variants remain classified as Variants of Uncertain Significance (VUS) pending more research.
Associated conditions
Biallelic pathogenic variants in COG6 cause a congenital disorder of glycosylation characterised by impaired protein glycosylation affecting multiple organ systems. Clinical presentations typically include developmental delay, intellectual disability, distinctive facial features, skeletal abnormalities and various organ system involvement. The severity and specific features can vary considerably between affected individuals, likely reflecting differences in residual COG complex function. Laboratory testing often reveals abnormal glycosylation patterns on serum proteins, which serves as a biochemical hallmark of these disorders.
No disease links recorded for this gene in our reference set.
Inheritance pattern
Conditions caused by pathogenic COG6 variants typically follow autosomal recessive inheritance.
When both parents are carriers, each child has a 25% chance of being affected, 50% of being a carrier, and 25% of being unaffected.
UK clinical status
COG6 appears on several NHS Genomic Medicine Service gene panels, reflecting its recognised role in inherited metabolic and developmental conditions. The gene is included on the Congenital Disorders of Glycosylation panel, the Intellectual Disability panel, the Likely Inborn Error of Metabolism panel and the Undiagnosed Metabolic Disorders panel, all with green classification indicating strong evidence for clinical validity. It also features on the Fetal Anomalies panel. These panel memberships support the use of COG6 sequencing in diagnostic pathways for individuals with unexplained developmental features, metabolic abnormalities or glycosylation defects identified through biochemical screening.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What does it mean to be a carrier of a COG6 variant?
Carriers possess one pathogenic variant and one typical copy of COG6. They generally remain healthy because the single functional copy provides sufficient protein for normal glycosylation. Carriers can, however, pass their variant to children.
How is COG6-related glycosylation disorder diagnosed?
Diagnosis typically combines clinical assessment, biochemical testing showing abnormal glycosylation patterns on serum proteins and genetic testing confirming biallelic pathogenic variants in COG6. Specialist metabolic and genetic services coordinate the diagnostic process.
Why is COG6 important for development?
The protein ensures proper glycosylation of numerous proteins essential for brain development, skeletal formation and organ function. Disrupted glycosylation during foetal and early postnatal development leads to the multi-system features observed in affected individuals.